Photographic products and processes comprising alkali-hydrolyzable antifoggant precursors

ABSTRACT

ANTIFOGGANT PRECURSORS OF THE FORMULA A-Z, WHEREIN A IS AN ANTIFOGGANT NUCLEUS RESULTANT FROM THE DEPROTONIZATION OF THE ANTIFOGGANT A-H, AND ZIS A MOIETY WHICH MASKS THE ANTIFOGGANT FUNCTIONALITY OF A, PROVIDE SUBSTANTIALLY NO ANTIFOGGANT EFFECT ON PHOTOGRAPHIC SYSTEMS IN WHICH THEY ARE CONTAINED UNTIL CLEAVAGE OF THE MASKING MOIETY FROM THE ANTIFOGGANT NUCLEUS IS ACCOMPLISHED.

April 20, 1m

7 PHOTOGRA ALKALI Filed 5. M. BLOOM PHIC PRODUCTS AND PRO -HYDROLYZABLEANTIFOG Sept. 5, 1968 LSUPPORT FCYAN DYE DEVELOPER LAYER RED SENSITIVESlLVER HALIDE EMULSION LAYER PINTER LAYER I- MAGENTA DYE DEVELOPER LAYERGREEN SENSITIVE SILVER HALIDE EMULSION LAYER INTERLAYER EVYELLOW DYEDEVELOPER LAYER BLUE NSITIV ILVER HALIDE EMuL N LAY FAUXILIARY LAYERUNLL AQUEOUS ALKALINE PROCESSING COMPOSITION v -\MAGE-RECEIVING LAYERSPACER LAYER NEUTRALlZl NG LAYER ombmwmzwn ATTORNEYS United StatesPatent U.S. Cl. 96-3 33 Claims ABSTRACT OF THE DISCLOSURE Antifoggantprecursors of the Formula AZ, wherein A is an antifoggant nucleusresultant from the deprotonization of the antifoggant A-H, and Z is amoiety which masks the antifoggant functionality of A, providesubstantially no antifoggant effect on photographic systems in whichthey are contained until cleavage of the masking moiety from theantifoggant nucleus is accomplished.

The present invention relates to photography and more particularly tophotographic products and processes.

It has been extensively reported in literature pertaining to photographythat photosensitive silver halide emulsions, and particularlyphotosensitive gelatino-silver halide emulsions, have a tendency to losesensitivity and to become spontaneously developable without exposure tolight. This phenomenon, characterized as chemical fog, may be defined asthe density above base level that is developed in emulsion areas thathave received no intentional exposure and, in general, is not uniformlydistributed over a selectively photoexposed emulsion, being greatest inthe unexposed areas and decreasing with increased exposure in anon-linear manner.

In both silver and color photographic systems, the latter where silverhalides are used to control image dye formation, fog results in a lossof image acuity.

Chemical fog may be divided into two classes: inherent fog, that is, fogwhich is emulsion initiated; and induced fog, that is, fog which isinitiated during development. Induced fog appears to be due to physicaldevelopment about extra-granular centers and inherent fog is probablydue to the presence of grains bearing a catalytic site sensitivity speck'which is unavoidably introduced and which is equivalent in itsproperties to latent image. Induced fog accordingly may be unaffected bythe level of inherent fog. Thus it will be readily appreciated that anemulsion susceptible to the development of chemical fog requires silverhalide grains possessing a catalytic center of sufiicient size to bespontaneously developable and/or grains unprotected fromnon-discriminatory development.

Various and sundry procedures and additives have been disclosed in theart to provide an increase in the stability of photosensitive silverhalide emulsions by reducing the tendency of photosensitive compositionsto fog. These procedures usually increase the speed-to-fog ratio;otherwise there would be no point in using them unless the requirementfor a low fog level completely overrides that for sensitivity. Ingeneral, the methods available for the control of fog are to increasethe bromide ion concentration during the emulsion fabrication process;select fog free gelatins, i.e., gelatins which are free of foggingcontaminants and which have desirable ratios of restrainer tosensitizer; reduce the level of chemical sensitization; and addinorganic or organic fog retarding adjuncts.

This invention relates primarily to the latter item above, and moreparticularly to the use of a specified class of organic antifoggantprecursors.

Accordingly, it is a primary object of the present invention to providenovel photographic products, and processes utilizing same, which exhibitdecreased susceptibility to fog formation.

Another object of the present invention is to provide novel processesand products, particularly adapted for obtaining monochromatic andmultichromatic images by diffusion transfer, which exhibit decreased fogformation throughout an extended temperature range.

A still further object of the present invention is to provide novelphotographic elements comprising not less than one silver halideemulsion having associated therewith specified transfer image-formingcomponents which exhibit increased effective processing temperaturelatitude.

Another object of the instant invention is to provide novel antifoggantprecursors for use in photographic environments, said antifoggantprecursors possessing substantially no antifoggant properties untilcontacted with a processing composition.

A further object of the instant invention is to provide a mechanismwhereby the active site on an antifoggant compound is masked until saidcompound is contacted with an alkaline processing solution.

An additional object of the present invention is to provide novelhydrolyzable compounds which possess antifoggant properties only intheir hydrolyzed state.

Another object of the present invention is to minimize changes in filmspeed of a given photographic system as a function of temperature and tocontrol fog of said system throughout the operating temperature rangethereof.

Other objects of the instant invention will in part be obvious and willin part appear hereinafter.

The invention accordingly comprises the process involving the severalsteps and the relation and order of one or more of such steps withrespect to each of the others and the product possessing the features,properties and the relation of the elements which are exemplified in thefollowing detailed disclosure and the scope of the application of whichwill be indicated in the claims.

For a fuller understanding of the nature and objects of the inventionreference should be had to the following detailed description taken inconnection with the accompanying drawing wherein:

FIG. 1 is a diagrammatic enlarged cross-sectional view of one embodimentof a film unit for obtaining multicolor images by a diffusion transferphotographic process illustrating the association of elements during onestage of the performance of a diffusion transfer process, the thicknessof the various materials being exaggerated.

In diffusion transfer processes for the formation of transfer images, anexposed photographic emulsion is developed and, substantiallyconcurrently therewith, an imagewise distribution of transferimage-forming components is provided as a function of the point-to-pointdegree of development. At least part of that imagewise distribution istransferred by diffusion to a contiguous imagereceiving layer to providethe desired transfer image formation to that layer.

In diffusion transfer processes for the formation of silver transferimages, an exposed silver halide emulsion is developed and,substantially concurrently therewith, an imagewise distribution ofsoluble silver complex is obtained by reaction of a silver solvent withsilver halide of the emulsion as a function of its point-to-point degreeof exposure. Preferably, the photosensitive silver halide emulsion isdeveloped with a viscous processing composition which is spread betweenan element comprising the silver halide emulsion and a print-receivingelement comprising a suitable silver precipitating layer. The processingcomposition affects development of the emulsion and substantiallysimultaneously therewith forms a soluble silver complex, for example, athiosulfate or thiocyanate, as

a function of the point-to-point degree of emulsion exposure. Thissoluble silver complex is, at least in part, transported in thedirection of the print receiving element and the silver thereof islargely precipitated in the silver precipitating layer of said elementto form a transfer image therein.

U.S. Pats. Nos. 2,647,049; 2,661,293; 2,698,798; and 2,802,735 disclosesubtractive color diffusion transfer processes wherein color couplingtechniques are utilized which comprise, at least in part, reacting oneor more developing agents and one or more color formers, as a functionof the photoexposure of a photographic emulsion, to provide a colorimage to a superposed image-receiving layer. U.S. Pat. No. 3,019,124discloses the manufacture of photographic color screen elementsparticularly adapted for employment in multicolor diffusion transferprocesses; and U.S. Pats. Nos. 2,968,554 and 2,983,606 disclosediffusion transfer processes where in a color screen element is utilizedto provide a multicolor transfer image to a superposed image-receivinglayer. U.S. Pats. Nos. 2,774,668; 2,983,606; and 3,345,163 disclosediffusion transfer processes wherein complete dyes are utilized toprovide a color transfer image to a superposed imagereceiving layer.

As disclosed in the aforementioned U.S. Pat. No. 2,983,606, aphotosensitive element containing a dye developer and a silver halideemulsion is exposed and wetted by a liquid processing composition, forexample, by emersion, coating, spraying, flowing, etc., in the dark, andthe exposed photosensitive element is superposed prior to, during orafter wetting on a sheet-like support element which may be utilized asan image-receiving element. In a preferred embodiment, the liquidprocessing composition is applied to the photosensitive element in asubstantially uniform layer as the photosensitive element is broughtinto superposed relationship with the image-receiving layer. The liquidprocessing composition permeates the emulsion to initiate development.The dye developer is immobilized or precipitated in, for example,exposed areas as a function of the development. Such immobilization isapparently, at least in part, due to a change in the solubilitycharacteristics of the dye developer upon oxidation; particularly withregard to its solubility in alkaline solutions. It may also be due inpart to a tanning effect on the emulsion by oxidized developing agentand in part to a localized exhaustion of alkali as a result ofdevelopment. In the exposed and partially exposed areas of the emulsion,the dye developer, unreacted and ditfusible, provides an imagewisedistribution of unoxidized dye developer dissolved in a liquidprocessing composition as a function of the point-to-point degree ofexposure of the silver halide emulsion. At least part of this imagewisedistribution of unoxidized dye developer is transferred by imbibition toa superposed image-receiving layer or element. Under certain conditionsthe layer of liquid processing composition may be utilized as theimagereceiving layer. The image-receiving element receives a depthwisediffusion of dye developer without appreciably disturbing the imagewisedistribution thereof to provide the color transfer image. Theimage-receiving element may contain agents adapted to mordant orotherwise fix dye developer. If the color of the transferred dyedeveloper is affected by change in the pH of the image-receivingelement, this pH may be adjusted to provide a pH affording the desiredcolor. The desired dye image carried by the image-receiving layer may beseparated from the photosensitive element by stripping at the end of asuitable imbibition period.

Dye developers are compounds which contain in the same molecule both thechromophoric system of a dye and also a silver halide developingfunction. By a silver halide developing function is meant a groupingadapted to develop exposed silver halide. A preferred silver halidedeveloping function is a hydroquinonyl group. Other suitable developingfunctions include ortho-dihydroxyphenyl and orthoand para-aminosubstituted hydroxy- 4 phenyl groups. In general, the developmentfunction includes a benzenoid developing function, that is, an aro maticdeveloping group which forms quinonoid or quinone substances whenoxidized.

An extensive compilation of such compounds is set forth in theaforementioned U.S. Pat. No. 2,983,606 and, in particular, in thevarious U.S. patents and copending applications incorporated byreference therein.

In general, the preferred dye developers comprise monoazo andanthraquinone dyes which possess one or two hydroquinonyl groupsattached to the auxochromophoric system of the dye by means of aconjugation-interrupting divalent group such as, for example, analkylene group.

Multicolored images may be obtained using color imageforming components,such as, for example, the previously mentioned dye developers, indiffusion transfer processes, by several techniques. One such techniquecontemplates the use of a photosensitive silver halide stratumcomprising at least two sets of selectively sensitized minutephotosensitive elements arranged in the form of a photosensitive screen.Transfer processes of this type are disclosed in the previously notedU.S. Pat. No. 2,983,606. In such an embodiment each of the minutephotosensitive elements has associated therewith an appropriate dyedeveloper in or behind a silver halide emulsion portion. In general, asuitable photosensitive screen prepared in accordance with thedisclosure of said patent comprises minute red sensitized emulsionelements, minute green sensitized emulsion elements and minute bluesensitized emulsion elements arranged in side-by-side relationship in ascreen pattern and having associated therewith, respectively, a cyan dyedeveloper, a magenta dye developer and a yellow dye developer.

Another process for obtaining multicolor transfer images utilizing dyedevelopers employs an integral multilayer photosensitive element such asis disclosed in the aforementioned U.S. Pats. Nos. 2,983,606 and3,345,163, wherein at least two selectively sensitized photosensitivestrata and associated dye developers are superposed on a single supportand are processed simultaneously and without separation with a singlecommon image-receiving layer. A suitable arrangement of this typecomprises a support carrying a red-sensitive silver halide emulsionstratum, a green-sensitive silver halide emulsion stratum, and ablue-sensitive silver halide emulsion stratum, said emulsions havingassociated therewith respectively, for example, a cyan dye developer, amagenta dye developer and a yellow dye developer. The dye developer maybe utilized in the silver halide emulsion layer, for example, in theform of particles, or it may be employed as a layer behind theappropriate silver halide emulsion stratum, for example, a layer of dyedeveloper applied by the use of a coating solution containing about 0.5to 8%, by weight, of the respective dye developer. Each set of silverhalide emulsion and associated dye developer strata may be separatedfrom other sets by suitable interlayers, for example, gelatin and thesynthetic polymeric materials disclosed in copending application ofLloyd D. Taylor, Ser. No. 641,669, filed May 26, 1967, now U.S. Pat. No.3,421,892. In certain instances it may be desirable to incorporate ayellow filter in front of the green-sensitive emulsion and such yellowfilter may be incorporated in an interlayer. However, where desirable, ayellow dye developer of appropriate spectral characteristics which ispresent in a state capable of functioning as a yellow filter may beemployed. In such instances a separate yellow filter may be omitted.

The preceding color image-forming components, that is, dye developers,are preferably selected for their ability to provide colors that areuseful in carrying out subtractive color photography, i.e., cyan,magenta and yellow. It should be noted that it is within the scope ofthis invention to use mixtures of dye developers, for example, to obtaina desired color, e.g., black. Thus, it is to be understood that theexpression color as used herein is intended to include the use of aplurality of colors to obtain black, as well as the use of a singleblack dye developer.

United States Pat. No. 3,362,819, issued on Jan. 9, 1968, to Dr. EdwinH. Land, discloses image-receiving elements, particularly adapted foremployment in color diffusion transfer processes, for example, of thetype disclosed in aforementioned U.S. Pat. No. 2,983,606, whichcomprises a support layer possessing on one surface thereof, insequence, a polymeric acid layer, a timing layer or spacer layer in thepreferred embodiment, and an imagereceiving layer adapted to provide avisible image upon transfer to said layer of diifusible dyeimage-forming substance.

As set forth in the last-mentioned application, the polymeric acid layercomprises polymers which contain acid groups, such as carboxylic acidand sulfonic acid groups, which are capable of forming salts with alkalimetals, such as sodium, potassium, etc., or with organic bases,particularly quaternary ammonium bases, such as tetramethyl ammoniumhydroxide, or potentially acid-yielding groups, such as anhydrides orlactones, or other groups which are capable of reacting with bases tocapture and retain them. The acid-reacting group is, of course,nondiffusible from the acid polymer layer. In the preferred embodimentsdisclosed, the acid polymer contains free carboxyl groups and thetransfer processing composition employed contains a large concentrationof sodium and/ or potassium ions. The acid polymers stated to be mostuseful are characterized by containing free carboxyl groups, beinginsoluble in water in the free acid form, and by forming water-solublesodium and/or potassium salts. One may also employ polymers containingcarboxylic acid anhydride groups, at least some of which preferably havebeen converted to free carboxyl groups prior to imbibition. While themost readily available polymeric acids are derivatives of cellulose orof vinyl polymers, polymeric acids from other classes of polymers may beused.

The acid polymer layer is disclosed to contain at least sufficient acidgroups to effect a reduction in the pH of the image layer from a pH ofabout 12 to 14 to a pH of at least 11 or lower at the end of theimbibition period, and preferably to a pH of about to 8 within a shorttime after imbibition. The pH of the processing composition employedpreferably is of the order of at least 12 to 14.

It is, of course, necessary that the action of the polymeric acid be socontrolled as not to interfere with either development of the negativeor image transfer of unoxidized dye developers. For this reason, the pHof the image layer is kept at a level of pH 12 to 14 until the positivedye image has been formed after which the pH is reduced very rapidly toat least about pH 11, and preferably about pH 9 to 10, before thepositive transfer image is separated and exposed to air. Unoxidized dyedevelopers containing hydroquinonyl developing radicals diffuse from thenegative to the positive as the sodium or other alkali salt. Thediffusion rate of such dye image-forming components thus is at leastpartly a function of the alkali concentration, and it is desired thatthe pH of the image layer remain on the order of 12 to 14 until transferof the necessary quantity of dye has been accomplished. The subsequentpH reduction, in addition to its desirable effect upon image lightstability, serves a highly valuable photographic function bysubstantially terminating further dye transfer. The processing techniquethus effectively minimizes changes in color balance as a result oflonger imbibition times in multicolor transfer processes usingmultilayer negatives.

The spacer layer of the last-mentioned copending application, forexample, an inert spacer layer comprising polyvinyl alcohol or gelatinor a temperature inversely permeable polymeric material as disclosed inconending U.S. application Ser. No. 447,100, filed Apr. 9, 1965, nowabandoned and replaced by continuation-in-part U.S. application Ser. No.664,503, filed on Aug. 30, 1967, and

now U.S. Pat. No. 3,455,686, acts to time control the pH reduction bythe polymeric acid layer. This timing is disclosed to be a function ofthe rate at which the alkali diffuses through the spacer layer. It wasstated to have been found that the pH does not drop until the alkali haspassed through the spacer layer, i.e., the pH is not reduced to anysignificant extent by the mere diffusion into the interlayer but the pHdrops quite rapidly once the alkali diffuses through the spacer layer.

As examples of materials, for use as the image-receiving layer, mentionmay be made of solution dyeable polymers such as nylon, as, for example,N-methoxymethyl polyhexamethylene adipamide; partially hydrolyzedpolyvinyl acetate; polyvinyl alcohol with or without plasticizers;cellulose acetate with fillers, as, for example, one-half celluloseacetate and one-half oleic acid; gelatin; and other materials of asimilar nature. Preferred materials comprise polyvinyl alcohol orgelatin containing a dye mordant such as poly-4-vinylpyridine, asdisclosed in U.S. Pat. No. 3,148,061.

As has been alluded to above, the presence of an antifoggant in aphotographic system may be responsible for reducing both inherent andinduced fog and will, therefore, produce a more attractive end product,both from aesthetic and technological points of view. Such productsdoubtless have a competitive advantage over other photographic productsnot quite as attractive or technologically efficient. The antifoggantcomposition is particularly helpful in minimizing or preventing reactionof a dye developer with unexposed silver halide and may be added to theprocessing composition and/or to one or more processingcomposition-permeable layers of the photosensitive and/orimage-receiving elements, The pertinent art has recognized manycompounds which have fog inhibiting characteristics, such as sodium andpotassium bromide and iodide, certain imidazoles, triazoles, tetrazoles,thiazoles, indazoles pyrazoles, pyrimidines, purines, etc.

At low temperatures, when processing composition is distributed upon thecontact surface of a selectively exposed photosensitive element of theaforementioned tripack configuration, development begins first in theblue-sensitive emulsion, since it contacts the processing compositionbefore the other layers. Temperature-retarded development, however, isslowed up even more by the restraining properties of antifoggant presentand results, for example, in increased uncontrolled yellow dye developertransfer from the blue-sensitive emulsion to the image-receiving layerbefore complete developmental control has been established. This causeswhat may be termed yellow stain. It will be evident that at hightemperatures the precise opposite happens, that is, the development rateis accelerated to a point where the restraining effect of theantifoggant is of insufficient consequence. The blue-sensitive emulsionwill then be developed and the properly developed silver, combined withthe fog present, will cause an over-control and thereby hold back thedesired imagewise yellow dye diffusion and result in an undesired shiftin color balance of the transfer image.

It has now been discovered that a given antifogging composition may bemodified in such a way as to mask the primary site or sites responsiblefor the antifogging effect, said masking moieties preventing interactionbetween photosensitive silver halides and the antifogging composition.It has additionally been found that if such moieties are capable ofbeing removed from said compound by a mechanism such as, forexample,hydrolysis, the antifogging nucleus will then be available to act uponthe system. It will additionally be evident that such a hydrolysismechanism will be directly dependent upon the ambient temperature sincethe rate of hydrolysis is a direct function of temperature, said ratedoubling ap proximately every 10 C. increase in temperature. Suchhydrolyzable antifoggant precursors are preferably substantiallynondiffusible and at least substantially less diffusible in theirunhydrolyzed form than in their hydrolyzed form. Itis theorized that therate of hydrolysis of the said antifoggant precursors is dependent upontemperature, and, therefore, provides an effective means of controllingthe availability of antifoggant in a given photographic system andinsuring that development is carried out as unimpeded as possible byantifoggant effect in order to provide the optimum fog to image ratiowhich may be obtained at a given development temperature. It is alsoconsidered possible that, rather than the hydrolysis rate being thecritical factor, the primary stimulus for the temperature-dependentrelease effect achieved herein may be solution rate; that is, the rateof solution of antifoggant precursor in processing composition may bethe basic parameter in determining the amount of antifog gant availableto the system at any given time. It is to be understood that the precisemechanism through which antifoggant is released into a photographicenvironment has not been ascertained With certainty, Accordingly, thetheories propounded herein are considered to be mere suggestions ofpossible mechanisms of operation and in no way limit the scope of theinvention disclosed and claimed herein. Substantially any moiety which,upon hy drolysis, is capable of leaving the antifoggant nucleus intactmay be utilized provided said moiety imparts no deleterious effects uponthe antifoggant functionality. Among such antifogging precursors arethose disclosed and claimed in copending application of Jerome Reid andDavid Carlson filed on the same date as the instant application, U.S.Ser. No. 756,884 wherein metal-complexed antifoggant compounds aredisclosed and claimed.

While antifoggant precursors which are readily hydrolyzable in acidic,basic and neutral mediums are contemplated by the instant invention itis preferred to utilize compounds which are principally base hydrolyzedor, more specifically, which are hydrolyzed to a greater degree in basethan, for example, in water. The rate of release of such preferredcompounds should be directly proportional to the concentration ofhydroxyl ions, i.e., the higher the pH, the greater the rate ofhydrolysis, temperature being constant. In instances where theantifoggant precursor is substantially hydrolyzed by water, saidprecursor may be encapsulated by any known technique in a medium whichis saponified by, for example, alkali processing composition as, forexample, cellulose acetate, benzoic anhydride containing polymers, etc.and incorporated directly in the film unit to insure a long shelf life,

Generically speaking, the compounds included in the instant inventioncomprise antifoggant precursors which, prior to being activated, possesssubstantially no antifoggant properties; while after activation theysubstantially reduce fogging in a given silver halide photographicsystem. It is apparent that such precursors are extremely valuable in aphotographic system which is to be utilized throughout a wide processingtemperature range if their mechanism of activation is regulated as afunction of processing temperature.

The antifoggant precursors of the present invention may be visualizedwith respect to the formula:

where A is an antifoggant nucleus resultant from the deprotonization ofthe antifoggant AH, and Z is any moiety or moieties whose removalprovides the requisite activation to the antifoggant nucleus. Z,therefore, may be considered to be any substituent which blocks theantifoggant functionality of the A nucleus; while after removal of the Zmoiety or moieties the A nucleus is rendered effective as an antifoggantand the Z moiety or moieties are not deleterious to the antifoggantfunctionality of said antifoggant A.

A preferred subclass of antifoggant precursors within the context of thepresent invention may be visualized with respect to the formula:

wherein: Z is as described above and F is the nonmetallic atomsnecessary to complete a heterocyclic antifoggant nucleus. Specificallyincluded within the atoms comprising F are carbon, oxygen, selenium,sulfur, nitrogen, etc.

A further preferred group of antifoggant precursors within the abovesubclass may be visualized with reference to the formula:

X mi,

wherein: Y is carbon or nitrogen; X is nitrogen or CR, where R ishydrogen or lower alkyl, i.e., containing less than six carbon atoms;and Z is as described above.

It has been disclosed in U.S. patent application Ser. No. 689,611, ofHoward G. Rogers, filed on Dec. 11, 1967, and now US. Pat. No. 3,473,924that certain compounds which may be generically defined asazabenzimidazoles provide excellent antifoggant functionality tophotographic systems, and particularly diffusion transfer photographicsystems, and may be adapted for advantageous employment therein toprovide increased latitude at the temperature range which is consideredoperative for the given system. Such compounds have been found toinhibit the formation of fog with substantially no sacrifice in theeffective speed of the photographic process in which it is utilized.

It has been discovered that a certain class of antifoggant precursorsderived from the azabenzimidazole nucleus provides superior antifoggantactivity to a given photographic system only after hydrolysis of saidcompounds has occurred. These compounds may generically be representedby the formula:

wherein:

R is a selected from the group consisting of hydrogen and lower alkylgroups, i.e., containing less than six carbon atoms; and Z is any groupwhich is subject to cleavage from the azabenzimidazole nucleus byhydrolysis, as described above.

It will be appreciated particularly with reference to US. patentapplication Ser. No. 689,611 cited above, that the compounds representedby the two formulae next above may contain various substituents in the 5and/or 6 position which enhance the antifoggant functionality of thecompounds and are considered to be included within the scope of thepresent invention. More particularly, among the substituents which maybe substituted in the 5 and/ or 6 position are halogen, lower alkyl,e.g., containing less than six carbon atoms, nitro, amino, hydroxy,lower alkoxy, i.e., containing less than six carbon atoms, aryl,sulfonamido, and carboxamido groups, it being understood that suchsubstituents may together constitute the atoms necessary to complete acyclic structure, as, for example,

With regard to the substituent Z, it should be appreciated that the onlyrequisite for determining its constitution is that it be capable ofmasking the antifoggant functionality of the given antifoggant radicaluntil some stimulus for removal of said Z moiety, e.g., hydrolysis, isimparted to the system. Among the radicals most suitable for utilizationas the Z moiety are acyl and fl-acyl alkalene radicals. Exemplar-y ofsuch remova'ble radicals which are representative of Z are:

It has been theorized that the antifoggant compounds displaying thestrongest antifoggant activity possess weak electron donor moieties atthe and/or 6 position in the generic formula next above. Accordingly, inthe most preferred embodiments of the present invention substituents inthe 5 and/or 6 position should inherently be Weak electron doors. Itwill be additionally appreciated that R and any substituents which maybe in the 5 and/ or 6 position above are intended to encompassequivalents thereof including situations wherein the substituents in the5 and 6 position above are taken together to form an annulatedhydrocarbon ring system.

Illustrative of the compounds which may be utilized in the presentinvention are:

Q G to 0 foggants. For example, with respect to a typical color filmprocessing composition containing a conventional antifoggant, such asbenzotriazole and the like, generally in the order of about 2%, theantifoggants of the present invention may be added to the system with aconcomitant reduction in the percentage of or elimination of thebenzotriazole or like antifoggant. Under certain conditions utilizationof small amounts of a second antifoggant may be found desirable toprovide limited antifogging and restraining properties at very lowtemperatures.

In a preferred embodiment of the present invention, a photosensitiveelement is employed which is specifically adapted to provide for theproduction of a multicolor dye transfer image and comprises adimensionally stable support layer carrying at least two selectivelysensitized silver halide emulsion strata each having a dye developermaterial of predetermined color associated therewith which is solubleand diffusible in alkali at a first pH.

The preferred photosensitive image-receiving element comprises analkaline solution permeable polymeric layer dyeable by the dyedeveloper; a polymeric spacer layer comprising a polymer possessingdecreasing alkaline solution permeability with increasing temperature;an alkaline solution permeable polymeric acid layer containingsufficient acidifying groups to effect reduction, subsequent tosubstantial multicolor transfer dye image formation, of theimage-receiving element from the first pH to a second pH, at which thedye image-providing material is insoluble and nondiifusible; and adimensionally stable support layer.

The silver halide emulsions comprising the multicolor photosensitivelaminate preferably possess predominant spectral sensitivity to separateregions of the spectrum and each has associated therewith a dye, whichis a silver halide developing agent and is, most preferably,substantially soluble in the reduced form only at the first pH,possessing a spectral absorption range substantially complementary tothe predominant sensitivity range of its associated emulsion. In thepreferred embodiment, each of the emulsion strata, and its associateddye, is separated from the remaining emulsion strata, and theirassociated dye, by separate alkaline solution permeable polymericinterlayers.

In such preferred embodiment of the invention, the silver halideemulsion comprises photosensitive silver halide dispersed in gelatin andis about 0.6 to 6 microns in thickness; the dye itself is dispersed inan aqueous alkaline solution polymeric binder, preferably gelatin, as aseparate layer about 1 to 7 microns in thickness; the alkaline solutionpermeable polymeric interlayers, preferably gelatin, are about 1 tomicrons in thickness; the alkaline solution permeable and dyeablepolymeric layer is transparent and about 0.25 to 0.4 mil. in thickness;the polymeric spacer layer intermediate the dyeable polymeric layer andthe polymeric acid layer is transparent and about 0.1 to 0.7 mil. inthickness; the alkaline solution permeable polymeric acid layer istransparent and about 0.3 to 1.5 mils. in thickness; and each of thedimensionally stable support layers are alkaline solution impermeableand about 2 to 6 mils. in thickness. It will be specifically recognizedthat the relative dimensions recited above may be appropriatelymodified, in accordance with the desires of the operator, with respectto the specific product to be ultimately prepared.

In the preferred embodiment of the present inventions film unit for theproduction of a multicolor transfer image, the respective silverhalide/dye developer units of the photosensitive element will be in theform of a tripack configuration which will ordinarily comprise a cyandye developer/red-sensitive emulsion unit contiguous the dimensionallystable support layer, the yellow dye developer/blue-sensitive emulsionunit most distant from the support layer and the magenta dyedeveloper/green-sensitive emulsion unit intermediate those units,recognizing 12 that the relative order of such units may be varied inaccordance with the desires of the operator.

Reference is now made to FIG. 1 of the drawings wherein there isillustrated a preferred film unit of the present invention.

As illustrated in FIG. 1, film unit 10 comprises a photosensitivelaminate 11 including, in order, dimensionally stable support layer 12,preferably a flexible sheet material; cyan dye developer layer 13;red-sensitive silver halide emulsion layer 14; interlayer 15; magentadye developer layer 16; green-sensitive silver halide emulsion layer 17;interlayer 18; yellow dye developer layer 19; blue-sensitive silverhalide emulsion layer 20; auxiliary layer 21, which may contain anauxiliary silver halide developing agent; and an image-receiving element22, including image-receiving layer 23; spacer layer 24; neutralizinglayer 25; and dimensionally stable support layer 26, preferably aflexible sheet material.

As shown in the drawing, the multilayer exposed photosensitive element11 is shown in processing relationship with an image-receiving element22 and a layer 27 of processing solution distributed intermediateelements 11 and 22.

In the performance of a diffusion transfer multicolor process employingfilm unit 10, the unit is exposed to radiation, actinic tophotosensitive laminate 11.

Subsequent to exposure, film unit 10 may be processed by being passedthrough opposed suitably gapped rolls in order to apply compressivepressure to a frangible container in order and to effect rupture of thecontainer and distribution of alkaline processing composition 27, havinga pH at which the cyan, magenta and yellow dye developers are solubleand diffusible, intermediate dyeable polymeric layer 23 and auxiliarylayer 21.

Alkaline processing solution 27 permeates emulsion layers 14, 17 and 20to initiate development of the latent images contained in the respectiveemulsions. The cyan, magneta and yellow dye developers, of layers 14, 17and 20, are immobilized, as a function of the development of theirrespective associated silver halide emulsions, preferably substantiallyas a result of their conversion from the reduced form to theirrelatively insoluble and nondilfusible oxidized form, thereby providingimagewise distributions of mobile, soluble and diffusible cyan, magentaand yellow dye developer, as a function of the point-topoint degree oftheir associated emulsions exposure. At least part of the imagewisedistributions of mobile cyan, magenta and yellow dye developertransfers, by diffusion, to aqueous alkaline solution permeablepolymeric layer 23 to provide a multicolor dye transfer image to thatlayer. Subsequent to substantial transfer image formation, a sufiicientportion of the ions comprising aqueous alkaline solution 27 transfers,by diffusion, through permeable polymeric layer 23, permeable spacerlayer 24, and to permeable polymeric acid layer 25, whereby alkalinesolution 27 decreases in pH, as a function of neutralization, to a pH atwhich the cyan, magenta and yellow dye developers, in the reduced form,are insoluble and nondilfusible, to provide thereby a stable multicolordye transfer image.

Subsequent to substantial transfer image formation, print-receivingelement 22 may be manually dissociated from the remainder of the filmunit, for example, by stripping.

The following examples are considered illustrative only and should notbe taken in a limiting sense.

EXAMPLE 1 The compound, 1-(2'-hydroxy benzoyl)benzimidazole,

was synthesized according to the following procedure:

3 gms. of benzimidazole were suspended in ethyl acetate and 5.25 gms. ofZ-hydroxybenzoyl chloride was dissolved in ethyl acetate and addedportionwise to the benzimidazole. The reactants Were stirred at roomtemperature overnight. The mixture was then heated and filtered toremove the insoluble benzimidazole hydrochloride. The filtrate wasevaporated to dryness and recrystallized from chloroform to give a whitesolid with a melting point of 166 to 170 C.

EXAMPLE 2 The compound, 1 -'(4' propanesulfonamido benzoyl)benzimidazole,

was synthesized according to the following procedure:

14.2 gms. of propane sulfonyl chloride was added to 13.7 gms. of p-aminobenzoic acid in 100 ml. of pyridine. The reactants were stirred for twohours at room temperature and poured onto ice. The crude product wassuspended in boiling ethyl acetate. Next, enough methanol was added togive a clear solution. This solution, was treated with Norit, wasfiltered and concentrated. A white solid with a melting point over 250C. crystallized out. this was discarded and the filtrate was furtherconcentrated to a very small volume whereupon a tan solid with a meltingpoint of 174 to 175 C. crystallized out. The infrared spectrum of thismaterial was consistent with 4- propane sulfonamido benzoic acid. 24.3gms. of the 4-propane sulfonamido benzoic acid was heated with 40 gms.of phosphorous pentachloride to 150 C. As soon as the melt washomogeneous it was cooled and triturated with hexane to give a crudeproduct comprising 4-propane sulfonamido benzoyl chloride. The productwas recrystallized from a benzene/hexane solution to give a whitecrystalline product with a melting point of 125-126 C. 1.2 gms. ofbenzamidazole was then suspended in ethyl acetate and 1.3 gms. of4-propane sulfonamido benzoyl chloride was added portionwise. Themixture was stirred at room temperature for several hours, then heatedto reflux, and the benzimidazole hydrochloride was filtered off. Thefiltrate was concentrated to a small volume and a crude productcrystallized out. It was recrystallized from ethyl acetate/ acetone andwas found to have a melting point of 215- 217 C.

EXAMPLE 3 The compound, 1-(2-propanesulfonamido benzoyl) benzimidazole,

O: N \N hexane. The product, 2-propane sulfonamido benzoyl chloride wasrecrystallized from ethyl acetate in a Dry Ice bath and was a tan solidwith a melting point of 6365 C. 4 gms. of benzimidazole was thensuspended in ethyl acetate and 3.3 gms. of the 2-propane sulfonamidobenzoyl chloride was added portionwise. The reaction was stirredovernight, was filtered, and the filtrate concentrated. Next thefiltrate was dissolved in chloroform containing some oxalic acid. Thiswas stirred for a couple of hours and filtered. The filtrate wasconcentrated to give a dark oil. This dark oil was dissolved in ethylether leaving behind an insoluble residue. The ethyl ether solution wasconcentrated to give a yellow oil containing white crystals. The oil wasdissolved again in ethyl ether. This time it was dissolved leaving thecrystals behind. The ether solution was dried with magnesium sulfate,filtered, and concentrated to give a light yellow oil. The MMR and IRwere consistent with the consigned structure of the 1-(2'-propanesulfonamido benzoyl)benzimidazole.

EXAMPLE 4 The compound 6 bromo3-(4'-hexadecane-sulfonamidobenzoyl)-5-methyl-4-azabenzimidazole,

was made according to the following procedure: 23.3 gms. of4-amino-benzoic acid was dissolved in 350 ml. of pyridine while keepingthe temperature at 5 C. 50 gms. of lhexadecanesulfonyl chloride wasadded portionwise waiting after each addition until it had all reactedand gone into solution. The total time of addition was 10 hours. Afterthe addition was completed the mixture was stirred at room temperaturefor 16 hours, the pyridine was evaporated Off on a vacuum rotaryevaporator with a steam bath temperature of 60 C. The thick pink pastethat was obtained was dried in a vacuum oven then recrystallized frommethyl Cellosolve (400 ml.) obtaining a White pink solid. It wasrecrystallized once more from methyl Cellosolve and 46.2 gms. of a whitesolid 4-hexadecane-sulfonamido-benzoic acid with a melting point of19l193 C. was obtained. 46 gms. of the 4-hexadecanesulfonamido-benzoicacid was suspended in 700 ml. of benzene and 15 gms. of oxalyl chloride,dissolved in 20 ml. of benzene, was added dropwise to the suspension.The mixture was heated at reflux temperature for 2 hours after whichthere still was undissolved solid. Two more gms. of oxalyl chloride wasadded and reflux was continued for another three hours. The reactionmixture was then cooled to room temperature. The small amount of solidpresent was filtered ofi" and the benzene was evaporated on a rotaryevaporator with a steam bath temperature of 50 C. To the resulting thickpaste about 200 ml. of petroleum ether was added giving a white solidwhich was repeatedly washed with petroleum ether. 42 gms. of solid4-hexadecane-sulfonamido-benzoyl chloride with a melting point of 7883C. was recovered. 19 gms. of 6-bromo-5- methyl 4 azabenzimidazole, 20gms. of 4 hexadecanesulfonamido-benzoyl chloride and 800-ml. of ethylacetate were mixed and allowed to stir at room temperature for 48 hours.The solution became quite thick after a couple of hours at which timeanother 200 ml. of ethyl acetate was added. The mixture was taken downto dryness then suspended in 1 l. of water. The solid was filtered OEand washed repeatedly with water. After drying, the solid in a vacuumoven it was recrystallized from 1,2-dimethoxyethane (about 500 ml.)twice. 9.7 gms. of 6- bromo-3-(4-hexadecane-sulfonamido-benzoyl)S-methyl- 4-azabenzimidazole with a melting point of 186187 C. wasrecovered.

15 EXAMPLE The compound 1 (4 hexadecanesulfonamidobenzoyl)4-benzotriazole,

was synthesized according to the following procedure: 5.9 gms. ofbenzotriazole, 8.5 gms. of 4-hexadecanesulfonamido-benzoyl chloride and400 ml. of ethyl acetate were mixed and stirred at room temperature for48 hours. The mixture was taken down to dryness, suspended in 1 l. ofwater, and the solid was filtered off. The solid was recrystallized froma mixture of 20% ethyl acetate, 80% ethanol, 7.6 gms. of1-(4-hexadecanesulfonamidobenzoyl) 4-benzotriazole with a melting pointof 142144 C. was recovered.

EXAMPLE 6 The compound 1 (4 hexadecanesulfonamidobenzoyl) benzimidazole,

was prepared according to the following procedure: To 30 ml. of ethylacetate 2 gms. of 4-hexadecanesulfonamidobenzoyl chloride was addedalong with 1.06 gms. of benzimidazole. The mixture was stirred for 24hours at room temperature, then evaporated to dryness at reducedpressure. The residue was mixed with 100 ml. of water and filtered. Theprecipitate, 1-(4-hexadecanesulfonamido benzoyl)benzimidazole wasrecrystallized from benzene and had a melting point of 164-165 C.

EXAMPLE 7 The compound 1-(4-hexanesulfonamidobenzoyl)benzimidazole,

was prepared according to the following procedure: To 500 ml. of benzenewas added 32.8 gms. of 4-hexanesulfonamidobenzoic acid. The mixture waspartially distilled to remove residual water. To the remaining slurrywas added ml. of oxalyl chloride and the mixture was refluxed 10 hoursto produce a clear solution. The solvent was distilled to dryness atreduced pressure to give a solid residue. To this was added 600 ml. ofdry ethyl acetate and, with stirring, 20.2 gms. of benzimidazole.Temperature rose to 35 C. After one hour the mixture was filtered. Theprecipitate was dried and washed with water and dried again. It weighed18.2 gms. The ethyl acetate filtrate was evaporated to dryness, theresidue was washed with water and dried, and then washed withdichloromethane. This weighed about 18 gms. It was combined with theabove solid and the whole recrystallized from a mixture of 20% ethylacetate and ethanol. 16.3 gms. of the1-(4-hexanesulfonamidobenzoyl)henzimidazole with a melting point of192-194 C. was recovered.

EXAMPLE 8 The compound, 1-[4'-[3"-(2'-methoxyethoxy)propanesulfonamido]benzoylJ-benzimidazole,

was prepared according to the following procedure: To 20 ml. of drybenzene was added 2 gms. of 4-[3'-(2"-methoxyethoxy)propane sulfonamido]benzoic acid (prepared by reacting methoxyethoxy propane sulfonylchloride with p-amino benzoic acid (see Example 2)) and 1.1 ml. ofovalyl chloride. The mixture was heated 1 hour at 80 C. and thendistilled under reduced pressure at 40 C. To the oily residue Was added25 ml. of ethyl acetate and 1.49 gms. of benzimidazole. After 1 hourstirring the mixture was filtered and the filtrate evaporated todryness. The combined precipitate and residue was Washed first withwater then with dilute hydrochloric acid, then again with water. Theundissolved solid was dried and recrystallized from1,1-2,2-tetrachloroethane. 1.51 gms. of 1 [4' [3" (2"'-methoxyethoxy)propane sulfonamido] benzoyl1benzimidazole with a melting point of 163-165 C. was recovered.

EXAMPLE 9 An image-receiving element was prepared by coating a cellulosenitrate subcoated baryta paper with the partial butyl ester ofpolyethylene/maleic anhydride copolymer prepared by refluxing, for 14hours, 300 gms. of DX- 840-31 Resin [trade name of Monsanto ChemicalCo., St. Louis, Mo'., for high viscosity poly-(ethylene/maleicanhydride)], gms. of n-butyl alcohol and 1 cc. of 85% phosphoric acid toprovide a polymeric acid layer approximately 0.3 mil thick. The externalsurface of the acid layer was coated with a 1% solution of polyvinylalcohol in water to provide a polymeric spacer layer approximately 0.30mil thick. The external surface of the spacer layer was then coated witha 2:1 mixture, by weight, of polyvinyl alcohol and poly-4-vinylpyridine,at a coverage of approximately 600 mgs. per square foot, to provide apolymeric image-receiving layer approximately 0.40 mil thick. Thethus-prepared image-receiving element was then baked at 180 F. for 30minutes and then allowed to cool.

A multicolor, multilayer photosensitive element was prepared in a mannersimilar to that disclosed in the aforementioned US. Pat. No. 3,345,163and detailed hereinbefore. In general, the photosensitive elementscomprised a support carrying a red-sensitive silver halide emulsionstratum, a green-sensitive silver halide emulsion stratum and ablue-sensitive silver halide emulsion stratum. In turn, the emulsionshad dispersed behind them in water-immiscible organic solvents andcontained in separate gelatin polymeric layers, respectively, a cyan dyedeveloper, a magenta dye developer and a yellow dye developer. Apolymeric interlayer was positioned between the yellow dye developedlayer and the greensensitive emulsion stratum, and also between themagenta dye developer layer and the red-sensitive emulsion stratum. Theparticular dye developers employed in the photosensitive elements were1,4-bis-(a-methyl-fi-hydroquinonyl-ethylamino) 5,8dihydroxyanthraquinone (a cyan dye developers);2-(p-[2,5-dihydroxyphenethyl]- phenylazo)-4-isopropoxy-1-naphthol (amagenta dye developer); and1-phenyl-3-n-hexyl-carbamyl-4-(p-[hydroquinonylethyl]-phenylazo)-5-pyrazolone(a yellow dye developer). The last-mentioned yellow and magenta dyedevelopers are disclosed in US. Pat. No. 3,134,764 and the cyan dyedeveloper is disclosed in US. Pat. No. 3,135,606.

In order to demonstrate the unique advantages of the present invention,comparative studies utilizing S-methyl- 6-bromo-4-azabenzimidazoleantifoggant, which is disclosed in the above-mentioned US. applicationof Howard G. Rogers, Ser. No. 689,611, was utilized in a givendifiFusion transfer photographic system is unmasked and masked formaccording to the teachings of the present invention. In addition, as acontrol, the same photographic process was utilized without anyantifoggant in the system. In order to appreciate the temperaturelatitude characteristics which may be achieved according to the instantinvention, tests were carried out at 50, 75 and 100 F.

Initially a negative manufactured as described above, is overcoated witha thin layer of gelatin at a weight of .014 gm. per square foot ofnegative material. The negatives which are to be utilized in testing themasked antifoggant, instead of being overcoated merely with gelatin,contain in the overcoat an additional .014 gm. of hydrolyzableantifoggant precursor which, in this case is, 6-brorno-3 (4'hexadecanesulfonamido benzoyl)-5- methyl-4-azabenzimidazole. Thedeveloping solution utilized in the system containing the antifoggantprecursor is identical to that utilized in the system containing noantifoggant and comprises:

Water--95 cc.

Hydroxyethyl cellulose-3.8 gms. Potassium hydroxide-40 gms.Benzyl-a-picolinium bromide-2.5 gms.

The system which contains a viable antifoggant initially is treated witha developing composition identical to that above with the exception that0.344 gms. of the antifoggant, S-methyl-6 bromo-4-azabenzimidazole, isincluded therein.

All of the multicolor photosensitive negative elements were exposed to astep-wedge to selectively filtered radiation and processed by spreadingthe aqueous liquid proc essing composition between said multicolornegative elements and image-receiving elements manufactured as describedabove as they were brought into superposed relationship in the absenceof actinic radiation. After an imbibition of one minute in the caseswhere the development was carried out at 75 and 100 F., and 2 minutes,seconds when the development was carried out at 50 F. theimage-receiving element was separated from the remainder of thefilm-assembly. The following tabulations collectively and succinctlypresents the results achieved during the instant comparative testing.

COMPARATIVE STUDY AT 50 F.

System containing 6-bromo-3- (4-hexadecane 1 0.6 reflection density ongreen curve.

COMPARATIVE STUDY AT 75 F.

System contain ing 6-bromo-3 System with (4'-hexadeeane System 5methyl-6 sulfonamido without bromo-4-azabenzoyl)-5- antibenzimidazole4-azafoggant antifoggant benzimidazole Relative speed 1 1. 11 1. 37

Dm; Divergence--. 21 72 .42

1 0.6 reflection density on green curve.

2 Not available.

COMPARATIVE STUDY AT F.

System containing 6bromo-3- 1 0.6 reflection density on green curve.

2 Not available.

In the 75 and 100 F. comparative evaluations the system containing noantifoggant was substantially inviable and never achieves the .6ordinate on the reflection density scale due to uncontrolled formationof fog, which is incident from the D information for this system. Itwill be initially recognized that the presence of the hydrolyzableantifoggant precursor has substantially no inhibiting effect on the filmat 50 F. The speed is approximately the same as the system withoutantifog gants while the D s are greater and the D s are smaller. Whencompared with the system containing a viable antifoggant it is notedthat the use of the antifoggant precursor produces a marked increase inspeed as well as a substantial decrease in stain, or D At 75 F.utilization of the masked antifoggant again provides higher speed to thesystem and substantially less stain which is likewise true at 100 F. Offurther consequence is the fact that the color divergence, that is, theordinate difference between the color curve having the highest D and thecolor curve having the lowest D is, in all instances, less when theantifoggant precursor is utilized than when the initially viableantifoggant is employed. The divergence in the control can besubstantially discounted because of the extremely low reflectiondensities achieved. It will be evident from a consideration of thetemperature-speed-D relationship depicted in the above comparativecharts that in the instance of the antifoggant precursor, very littleantifoggant is available in the cold temperatures, and more isprogressively released as the temperature increases to provide a filmproduct with a substantially constant speed over a wide temperaturerange.

It has been found that when the compounds of the present invention areincorporated directly into the photosensitive emulsion of a diifusiontransfer photographic product, a degree of stabilization is achieved.That is to say that substantially the same picture quality results witha newly made product as with a product which has been stored under otherthan reduced temperature conditions for an extended period. Accordingly,it will be appreciated that within the context of the present invention,stabilization properties may be anticipated with the incorporation ofthe herein disclosed antifoggant precursors in photographic emulsions asan unexpected bonus.

In general, the optimum concentration of the agent to be employed as anantifoggant precursor should be determined empirically for each givenspecific photographic system. A typical concentration range is between0.005 to 5.0 mgs. per mg. of silver halide present in the silver halideemulsion of concern depending on the fogging characteristics of saidemulsion. Although concentrations in excess of the given range may beemployed an increase in the concentration beyond certain empiricallimits generally provides no additional beneficial results. Conversely,concentrations below that of the designated range merely decrease fogcontrol at high temperatures below the effective levels generally soughtbut, nonetheless, do not negate the achievement of some beneficial fogcontrol.

The agents themselves may be initially disposed in any one or moreprocessing composition permeable layers of the film units photosensitiveand/or image-receiving elements, at any stage during their manufacture.

It will be appreciated that within the context of the present invention,the bulkiness" of specific antifoggant nucleus materials may be adjustedto provide an anchor ing or diffusion-inhibiting function within a givenphotographic system. Such a design might easily be applicable tosituations where it is desirable to localize antifoggant activity in theimmediate vicinity of a given emulsion in order to maintain a desiredantifoggant concentration range in the area of that emulsion. Moietieswhich have been found quite useful for this purpose are long chain fattyacid groups as, for example, octyl, stearyl, etc.

It should also be appreciated that the time within the development cycleat which the antifoggant composition sees the alkaline processingcomposition may be adjusted by judicious placement of said antifoggantwithin the photographic system. In this manner it will be seen that therelease of antifoggant for use in conjunction with a given emulsion maybe delayed until the end of the fog induction period in theantifoggant-associated emulsion.

The liquid processing composition referred to for effectingmonochromatic and multicolor transfer processes comprises at least anaqueous solution of an alkaline compound, for example, diethylamine,sodium hydroxide sodium carbonate, etc. and possesses a pH in excess of12 preferably. If the liquid processing composition is to be applied tothe emulsion by being spread thereon, preferably in a relatively thinuniform layer, it may include a viscosity-increasing compoundconstituting a film-forming material of the type which, when saidcomposition is spread and dried, forms a relatively firm and relativelystable film. A preferred film-forming material is a high molecularweight polymer such as a polymeric, watersoluble ether which is inert toan alkaline solution such as, for example, a hydroxyethyl cellulose orsodium carboxymethyl cellulose. Other film-forming materials orthickening agents whose ability to increase viscosity is substantiallyunaffected if left in solution for a long period of time may also beused. The film-forming material is preferably contained in theprocessing composition in suitable quantities to impart to saidcomposition a viscosity in excess of 1,000 centipoises at a temperatureof approximately 24 C. and preferably of the order of 1,000 to 200,000centipoises at said temperature. Illustrations of suitable liquidprocessing compositions may be found in the several patents andcopending applications herein mentioned and also in examples hereingiven. Under certain circumstances, it may be desirable to apply aliquid processing composition to the photosensitive element prior toexposure, in accordance with the technique described in US. Patent No.3,087,816, issued Apr. 30, 1963.

It will be noted that the liquid processing composition employed maycontain an auxiliary or accelerating developing agent, such asp-methylaminophenol, 2,4 diaminophenol, p-benzylaminophenol,hydroquinone, toluhydroquinone, phenylhydroquinone,4'-methylphenylhydroquinone, etc. It is also contemplated to employ aplurality of auxiliary or accelerating developing agents, such as a3-pyrazolidone developing agent and a benzenoid developing agent, asdisclosed in US. Pat. No. 3,039,869, issued June 19, 1962. As examplesof suitable combinations of auxiliary developing agents, mention may bemade of 1-phenyl-3-pyrazolidone in combination with p-benzylaminophenoland 1 phenyl-3-pyrazolidone in combination with 2,5bis-ethyleneimino-hydroquinone. Such auxiliary developing agents may beemployed in the liquid processing composition or they may be initiallyincorporated, at least in part, in one or more permeable strata of thefilm unit. It may be noted that at least a portion of the dye developeroxidized during development may be oxidized and immobilized as a resultof a reaction, e.g., an energy-transfer reaction, with the oxidationproduct of an oxidized auxiliary developing agent, the latter developingagent being ozidizedby the development of exposed silver halide. Such areaction of oxidized developing agent with unoxidized dye developerwould regenerate the auxiliary developing agent for further reactionwith the exposed silver halide.

In addition, development may be desirably effected in the presence of anonium compound, particularly a quaternary ammonium compound, inaccordance with the processes disclosed in Us. Pat. No. 3,173,786.

The support layers referred to may comprise any of the various types ofconventional rigid or flexible supports, for example, glass, paper,metal, and polymeric films of both synthetic types and those derivedfrom naturally occurring products. Suitable materials include paper;aluminum; polymethacrylic acid, methyl and ethylesters; vinyl chloridepolymers; polyvinyl acetal; polyamides such as nylon; polyesters such aspolymeric films derived from ethylene glycol terephthalic acid andcellulose derivatives such as cellulose acetate, triacetate, nitrate,propionate, butyrate, acetate-propionate, or acetate-butyrate.

It will be understood that silver halides of varying halideconcentrations may be advantageously employed and that the silver halideemulsions employed may be sensitized chemically and optically by any ofthe accepted procedures.

While a rupturable container provides a convenient means for spreading aliquid processing composition between layers of a film unit whereby topermit the processing to be carried out with a camera apparatus, thepractices of this invention may be otherwise effected. For example, aphotosensitive element, after exposure in suitable apparatus and whilepreventing further exposure thereafter to actinic light, may be removedfrom such apparatus and permeated with the liquid processingcomposition, as by coating the composition on said photosensitiveelement or otherwise wetting said element with the composition,following which the permeated, exposed photosensitive element, stillwithout additional exposure to actinic light, is brought into contactwith the image-receiving element for image formation in the mannerheretofore described.

In examples of this specification, percentages of components are givenby weight unless otherwise indicated.

Throughout the specification and claims, the expression superposing hasbeen used. This expression is intended to cover the arrangement of twolayers in overlying rela tion to each other either in face-to-facecontact or in separated condition and including between them at leastone layer or stratum of a material which may be a viscous liquid.

Since certain changes may be made in the above produts, compositions andprocesses without departing from the scope of the invention hereininvolved, it is intended that all matter contained in the abovedescription shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:

1. In a process for forming a photographic image which comprises thestep of developing an exposed photosensitive element containing a silverhalide emulsion with an aqueous alkaline processing composition, theimprovement which comprises conducting said process in the presence ofan effective concentration of a hydrolyzable antofoggant precursorcomprising an antifoggant nucleus possessing a deactivating group whichis removed by hydrolysis at a temperature-dependent rate upon beingcontacted with said processing composition, independent of exposure anddevelopment.

2. The process of claim 1 wherein said antifoggant precursor isrepresented by the formula:

wherein: A is an antifoggant nucleus possessing fog inhibitingproperties on said silver halide emulsion; and Z is an antifoggantdeactivating moiety which masks an active site of said antifoggantnucleus and is adapted to be removed upon contact with said processingcomposition, at a temperature-dependent rate.

3. The process of claim 2 wherein said antifoggant precursor isrepresented by the formula:

wherein: Z is an alkaline processing composition hydrolyzableantifoggant deactivating group and F is the nonmetallic atoms necessaryto complete a heterocyclic antifoggant nucleus.

4. The process of claim 3 wherein said antifoggant precursor isrepresented by the formula:

wherein: Y is CH or nitrogen; X is nitrogen or CR, where R is hydrogenor lower alkyl, i.e., containing less than six carbon atoms; and Z is analkaline processing composition hydrolyzable antifoggant deactivatinggroup.

5. The process of claim 4 wherein said antifoggant precursor isrepresented by the formula:

wherein: R is a hydrogen or lower alkyl group; and Z is an alkalineprocessing composition hydrolyzable antifoggant deactivating group.

6. The process of claim 5 wherein said process is conducted at atemperature within the range of about 50 to 100 7. The process of claim5 wherein said Z is an acyl or a p-acylalkalene group.

8. The process of claim 5 wherein said alkali hydrolyzable antifoggantprecursor is 6-bromo-3-(4-hexadecanesulfonamidobenzoyl)-5-methyl-4-azabenzimidazole.

9. The process of claim 5 which includes the steps of developing saidexposed photosensitive element with an aqueous alkaline diffusiontransfer processing composition forming thereby an imagewisedistribution of image-forming components in said hotosensitive elementas a function of the point-to-point degree of exposure thereof andtransferring at least part of said imagewise distribution by diffusionto a contiguous image-receiving layer to provide thereto a photographicdiffusion transfer image.

10. The process of claim 9 wherein said image-forming componentscomprise soluble silver complex.

11. The process of claim 9 wherein said image-forming componentscomprise image-forming materials.

12. The process of claim 10 wherein said color imageforming componentscomprise at least one dye which is a silver halide developing agent.

13. The process of claim 12 which includes, in combination, the steps ofexposing a photosensitive element which comprises at least twoselectively sensitized silver halide emulsion layers each having a dyeof predetermined color associated therewith, which dye is a silverhalide development of the latent images contained in each of saidtacting said exposed photosensitive element with an aqueous alkalineprocessing composition and effecting thereby hydrolytic removal of saidZ moiety from said antifoggant precursor as a function of processingtemperature and developmentof the latent images contained in each ofsaid silver halide emulsions, immobilizing the dye associated with eachof said emulsions as a result of said development and forming thereby animagewise distribution of mobile dye as a function of the point-to-pointdegree of exposure thereof, and transferring, by imbibition, at least aportion of each of said image wise distributions of mobile dye to asuperposed image-receiving element to provide thereto a multicolor dyetransfer image.

14. The process of claim 13 which includes, in combination, the steps ofexposing a photosensitive element comprising blue-sensitive,green-sensitive and red-sensitive gelatino silver halide emulsion layersmounted on a common support, each of said blue-sensitive,green-sensitive and red-sensitive silver halide emulsion layer havingassociated therewith, respectively, yellow, magenta and cyan dyes, eachof said dyes being a silver halide developing agent soluble anddiifusible in alkali; contacting said exposed photosensitive elementwith an aqueous alkaline processing composition effecting therebyhydrolytic removal of said Z moiety from said antifoggant precursor as afunction of processing temperature and development of the latent imagecontained in each silver halide emulsion; immobilizing said yellowmagenta and cyan dye as a function of development of their respectiveassociated silver halide emulsion forming thereby an imagewisedistribution of mobile yellow, magenta and cyan dye; and transferring,by imbibition, at least a portion of each of said imagewisedistributions of mobile dye to a superposed image-receiving element toprovide thereto a multicolor dye transfer image.

15. The process of claim 14 wherein said antifoggant precursor is6-bromo-3-(4'-hexadecane-sulmonamido benzoyl-5-methyl-4-azabenzimidazole.

16. The process of claim 14, wherein said process is conducted at atemperature within the range of about 50 to F.

17. As a product, photosensitive element which com prises a supportlayer carrying a photosensitive silver halide emulsion and havingassociated therewith a hydrolyzable antifoggant precursor of the formulaAZ, where A is an antifoggant nucleus of the antifoggant AH and Z is anantifoggant deactivating group, said antifoggant precursor being capableof releasing antifoggant at a temperaturedependent rate independent ofexposure and development.

18. The product of claim 17 wherein said antifoggant precursor isrepresented by the formula:

wherein Z is an alkaline processing composition hydrolyzable antifoggantdeactivating group and F is the nonmetallic atoms necessary to completea heterocyclic antifoggant nucleus.

19. The product of claim 18 wherein said antifoggant precursor isrepresented by the formula: AZ, wherein A comprises an antifoggantnucleus possessing fog inhibiting properties on said silver halideemulsion and Z is a moiety which deactivates the fog inhibitingproperties of said antifoggant nucleus and is adapted to be removed byhydrolysis upon contact with an alkaline processing composition.

20. The product of claim 19 wherein said antifoggant precursor isrepresented by the formula:

wherein: Y is CH or nitrogen; X is nitrogen or CR, where R is hydrogenor lower alkyl, and Z is an alkaline processing composition hydrolyzableantifoggant deactivating group.

21. The product of claim 20 wherein said antifoggant precursor isrepresented by the formula:

wherein: R is a hydrogen or lower alkyl group; and Z is an alkalineprocessing composition hydrolyzable antifoggant deactivating group.

22. The product of claim 21 wherein said Z is an acyl or B-acylalkalenegroup.

23. The product of claim 22 wherein said hydrolyzable antifoggantprecursor is6-bromo-3-(4-hexadecanesulfonamido-benzoyl)--methyl-4-azabenzimidazole.

24. The product of claim 21 wherein said silver halide emulsion has adye, which dye is a silver halide developing agent associated therewith.

25. The product of claim 24 wherein said dye is disposed in a separatelayer intermediate said silver halide emulsion and said support.

26. The product of claim 24 wherein said support layer carries on onesurface at least two selectively sensitized silver halide emulsionlayers each having a dye which dye is a silver halide developing agentof predetermined color associated therewith.

27. The product of claim 26 wherein each of said selectively sensitizedphotosensitive emulsion layers has predominant spectral sensitivity -toseparate regions of the spectrum and the dye associated with each ofsaid emulsion layers possesses a spectral absorption range substantially24 complementary to the predominant ensitivity range of its associatedemulsion layer.

28. The product of claim 27 wherein said photosensitive silver halideemulsion layers comprise, in sequence, a redsensitive silver halideemulsion layer, a green-sensitive silver halide emulsion layer and ablue-sensitive silver halide emulsion layer, having associatedtherewith, respectively, cyan, magenta and yellow dyes, each of saiddyes being silver halide developing agents.

29. The product of claim 21 which includes a diffusion transferimage-receiving element aflixed at least one edge of said photosensitiveelement.

30. The product of claim 29 which includes a rupturable containerretaining an aqueous alkaline processing composition afiixed one edge ofone of said photosensitive and said image-receiving elements and adaptedupon rupture to distribute its contents intermediate said photosensitiveelement and said image-receiving element upon superpositioning of saidelements.

31. The product of claim 27 wherein said antifoggant precursor isdispersed in a silver halide emulsion layer of the photosensitiveelement.

32. The product of claim 29 wherein said antifoggant precursor isdispersed in a layer on the image-receiving element.

33. The product of claim 28 wherein said hydrolyzable antifoggantprecursor is6-bromo-3-(4-hexadecanesulfonamido-benzoyl)-5-methyl-4-azabenzimidazole.

References Cited UNITED STATES PATENTS 3,148,062 9/1964 Whitmore, et al9655 3,227,554 1/1966 Barr, et al 9655 3,364,022 1/1968 Barr 9633,379,529 4/1968 Porter, et a1 96-36 3,455,686 l/l969 Farney, et a1 9633,473,924 10/1969 Rogers 96-29 NORMAN G. TORCHIN, Primary Examiner A. T.SURO PICO, Assistant Examiner US. Cl. X.R. 9666.5, 29

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent NO- 3,575,699 Dated A ril 20 l97l Inventor) Stanley M. Bloom and Howard G.Rogers It is certified that error appears in the above-identified patentand that said Letters Patent are hereby corrected as shown below:

Claim 11, line 2, after "comprise" insert -color-.

Claim 13, line 6, "velopment of the latent images contain in each ofsaid" should be veloping agent and is soluble and diffusible, in alkali,con- Claim 17, line 1, after "product," insert a.

Claim 18, line 1, delete "l8 and substitute therefor l delete "l7" andsubstitute therefor l8.

Claim 19, line 1, delete "l9." and substitute therefor delete "l8" andsubstitute therefor l7-.

Claim 21, line 3, cancel the formula and substitute therei N: L N/ RClaim 27, line 6, "ensitivity" should be sensitivity.

Signed and sealed this 21st day of November 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GO'I'TSCHALK Attesting Officer Commissionerof Pete

